Add support for login link

app/src/main/AndroidManifest.xml

@@ -34,11 +34,17 @@
                 android:value='androidx.startup' />
         </provider>
 
+        <!--
+        Using launchMode singleTask to avoid multiple instances of the Activity
+        when the app is already open. This is important for incoming share (see
+        https://github.com/element-hq/element-x-android/issues/4074) and for opening
+        the application from a mobile.element.io link.
+        -->
         <activity
             android:name=".MainActivity"
             android:configChanges="orientation|screenSize|screenLayout|keyboardHidden|uiMode"
             android:exported="true"
-            android:launchMode="singleTop"
+            android:launchMode="singleTask"
             android:theme="@style/Theme.ElementX.Splash"
             android:windowSoftInputMode="adjustResize">
             <intent-filter>
@@ -54,6 +60,9 @@
                     android:host="open"
                     android:scheme="elementx" />
             </intent-filter>
+            <!--
+              Oidc redirection
+            -->
             <intent-filter>
                 <action android:name="android.intent.action.VIEW" />
 
@@ -80,6 +89,21 @@
                 <!-- Matching asset file: https://staging.element.io/.well-known/assetlinks.json -->
                 <data android:host="staging.element.io" />
             </intent-filter>
+            <!--
+              Element mobile links
+              Example: https://mobile.element.io/element?account_provider=example.org&login_hint=mxid:@alice:example.org
+            -->
+            <intent-filter android:autoVerify="true">
+                <action android:name="android.intent.action.VIEW" />
+
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.BROWSABLE" />
+
+                <data android:scheme="https" />
+                <!-- Matching asset file: https://mobile.element.io/.well-known/assetlinks.json -->
+                <data android:host="mobile.element.io" />
+                <data android:path="/element" />
+            </intent-filter>
             <!--
               matrix.to links
               Note: On Android 12 and higher clicking a web link (that is not an Android App Link) always shows content in a web browser

appnav/build.gradle.kts

@@ -53,6 +53,7 @@ dependencies {
     testImplementation(libs.molecule.runtime)
     testImplementation(libs.test.truth)
     testImplementation(libs.test.turbine)
+    testImplementation(projects.features.login.test)
     testImplementation(projects.libraries.matrix.test)
     testImplementation(projects.libraries.oidc.impl)
     testImplementation(projects.libraries.preferences.test)

appnav/src/main/kotlin/io/element/android/appnav/NotLoggedInFlowNode.kt

@@ -24,8 +24,11 @@ import dagger.assisted.Assisted
 import dagger.assisted.AssistedInject
 import io.element.android.anvilannotations.ContributesNode
 import io.element.android.features.login.api.LoginEntryPoint
+import io.element.android.features.login.api.LoginParams
 import io.element.android.libraries.architecture.BackstackView
 import io.element.android.libraries.architecture.BaseFlowNode
+import io.element.android.libraries.architecture.NodeInputs
+import io.element.android.libraries.architecture.inputs
 import io.element.android.libraries.designsystem.utils.ForceOrientationInMobileDevices
 import io.element.android.libraries.designsystem.utils.ScreenOrientation
 import io.element.android.libraries.di.AppScope
@@ -46,10 +49,16 @@ class NotLoggedInFlowNode @AssistedInject constructor(
     buildContext = buildContext,
     plugins = plugins,
 ) {
+    data class Params(
+        val loginParams: LoginParams?,
+    ) : NodeInputs
+
     interface Callback : Plugin {
         fun onOpenBugReport()
     }
 
+    private val inputs = inputs<Params>()
+
     override fun onBuilt() {
         super.onBuilt()
         lifecycle.subscribe(
@@ -74,6 +83,12 @@ class NotLoggedInFlowNode @AssistedInject constructor(
                 }
                 loginEntryPoint
                     .nodeBuilder(this, buildContext)
+                    .params(
+                        LoginEntryPoint.Params(
+                            accountProvider = inputs.loginParams?.accountProvider,
+                            loginHint = inputs.loginParams?.loginHint,
+                        )
+                    )
                     .callback(callback)
                     .build()
             }

appnav/src/main/kotlin/io/element/android/appnav/RootFlowNode.kt

@@ -33,13 +33,16 @@ import io.element.android.appnav.intent.ResolvedIntent
 import io.element.android.appnav.root.RootNavStateFlowFactory
 import io.element.android.appnav.root.RootPresenter
 import io.element.android.appnav.root.RootView
+import io.element.android.features.enterprise.api.EnterpriseService
+import io.element.android.features.login.api.LoginParams
 import io.element.android.features.rageshake.api.bugreport.BugReportEntryPoint
 import io.element.android.features.signedout.api.SignedOutEntryPoint
 import io.element.android.features.viewfolder.api.ViewFolderEntryPoint
 import io.element.android.libraries.architecture.BackstackView
 import io.element.android.libraries.architecture.BaseFlowNode
 import io.element.android.libraries.architecture.createNode
 import io.element.android.libraries.architecture.waitForChildAttached
+import io.element.android.libraries.core.uri.ensureProtocol
 import io.element.android.libraries.deeplink.DeeplinkData
 import io.element.android.libraries.designsystem.theme.components.CircularProgressIndicator
 import io.element.android.libraries.di.AppScope
@@ -61,6 +64,7 @@ class RootFlowNode @AssistedInject constructor(
     @Assisted val buildContext: BuildContext,
     @Assisted plugins: List<Plugin>,
     private val authenticationService: MatrixAuthenticationService,
+    private val enterpriseService: EnterpriseService,
     private val navStateFlowFactory: RootNavStateFlowFactory,
     private val matrixSessionCache: MatrixSessionCache,
     private val presenter: RootPresenter,
@@ -99,14 +103,14 @@ class RootFlowNode @AssistedInject constructor(
                         if (navState.loggedInState.isTokenValid) {
                             tryToRestoreLatestSession(
                                 onSuccess = { sessionId -> switchToLoggedInFlow(sessionId, navState.cacheIndex) },
-                                onFailure = { switchToNotLoggedInFlow() }
+                                onFailure = { switchToNotLoggedInFlow(null) }
                             )
                         } else {
                             switchToSignedOutFlow(SessionId(navState.loggedInState.sessionId))
                         }
                     }
                     LoggedInState.NotLoggedIn -> {
-                        switchToNotLoggedInFlow()
+                        switchToNotLoggedInFlow(null)
                     }
                 }
             }
@@ -117,9 +121,9 @@ class RootFlowNode @AssistedInject constructor(
         backstack.safeRoot(NavTarget.LoggedInFlow(sessionId, navId))
     }
 
-    private fun switchToNotLoggedInFlow() {
+    private fun switchToNotLoggedInFlow(params: LoginParams?) {
         matrixSessionCache.removeAll()
-        backstack.safeRoot(NavTarget.NotLoggedInFlow)
+        backstack.safeRoot(NavTarget.NotLoggedInFlow(params))
     }
 
     private fun switchToSignedOutFlow(sessionId: SessionId) {
@@ -175,7 +179,9 @@ class RootFlowNode @AssistedInject constructor(
         data object SplashScreen : NavTarget
 
         @Parcelize
-        data object NotLoggedInFlow : NavTarget
+        data class NotLoggedInFlow(
+            val params: LoginParams?
+        ) : NavTarget
 
         @Parcelize
         data class LoggedInFlow(
@@ -211,13 +217,16 @@ class RootFlowNode @AssistedInject constructor(
                 }
                 createNode<LoggedInAppScopeFlowNode>(buildContext, plugins = listOf(inputs, callback))
             }
-            NavTarget.NotLoggedInFlow -> {
+            is NavTarget.NotLoggedInFlow -> {
                 val callback = object : NotLoggedInFlowNode.Callback {
                     override fun onOpenBugReport() {
                         backstack.push(NavTarget.BugReport)
                     }
                 }
-                createNode<NotLoggedInFlowNode>(buildContext, plugins = listOf(callback))
+                val params = NotLoggedInFlowNode.Params(
+                    loginParams = navTarget.params,
+                )
+                createNode<NotLoggedInFlowNode>(buildContext, plugins = listOf(params, callback))
             }
             is NavTarget.SignedOutFlow -> {
                 signedOutEntryPoint.nodeBuilder(this, buildContext)
@@ -272,18 +281,36 @@ class RootFlowNode @AssistedInject constructor(
         val resolvedIntent = intentResolver.resolve(intent) ?: return
         when (resolvedIntent) {
             is ResolvedIntent.Navigation -> navigateTo(resolvedIntent.deeplinkData)
+            is ResolvedIntent.Login -> onLoginLink(resolvedIntent.params)
             is ResolvedIntent.Oidc -> onOidcAction(resolvedIntent.oidcAction)
             is ResolvedIntent.Permalink -> navigateTo(resolvedIntent.permalinkData)
             is ResolvedIntent.IncomingShare -> onIncomingShare(resolvedIntent.intent)
         }
     }
 
+    private suspend fun onLoginLink(params: LoginParams) {
+        // Is there a session already?
+        val latestSessionId = authenticationService.getLatestSessionId()
+        if (latestSessionId == null) {
+            // No session, open login
+            if (enterpriseService.isAllowedToConnectToHomeserver(params.accountProvider.ensureProtocol())) {
+                switchToNotLoggedInFlow(params)
+            } else {
+                Timber.w("Login link ignored, we are not allowed to connect to the homeserver")
+                switchToNotLoggedInFlow(null)
+            }
+        } else {
+            // Just ignore the login link if we already have a session
+            Timber.w("Login link ignored, we already have a session")
+        }
+    }
+
     private suspend fun onIncomingShare(intent: Intent) {
         // Is there a session already?
         val latestSessionId = authenticationService.getLatestSessionId()
         if (latestSessionId == null) {
             // No session, open login
-            switchToNotLoggedInFlow()
+            switchToNotLoggedInFlow(null)
         } else {
             attachSession(latestSessionId)
                 .attachIncomingShare(intent)

appnav/src/main/kotlin/io/element/android/appnav/intent/IntentResolver.kt

@@ -8,6 +8,8 @@
 package io.element.android.appnav.intent
 
 import android.content.Intent
+import io.element.android.features.login.api.LoginIntentResolver
+import io.element.android.features.login.api.LoginParams
 import io.element.android.libraries.deeplink.DeeplinkData
 import io.element.android.libraries.deeplink.DeeplinkParser
 import io.element.android.libraries.matrix.api.permalink.PermalinkData
@@ -21,11 +23,13 @@ sealed interface ResolvedIntent {
     data class Navigation(val deeplinkData: DeeplinkData) : ResolvedIntent
     data class Oidc(val oidcAction: OidcAction) : ResolvedIntent
     data class Permalink(val permalinkData: PermalinkData) : ResolvedIntent
+    data class Login(val params: LoginParams) : ResolvedIntent
     data class IncomingShare(val intent: Intent) : ResolvedIntent
 }
 
 class IntentResolver @Inject constructor(
     private val deeplinkParser: DeeplinkParser,
+    private val loginIntentResolver: LoginIntentResolver,
     private val oidcIntentResolver: OidcIntentResolver,
     private val permalinkParser: PermalinkParser,
 ) {
@@ -40,10 +44,17 @@ class IntentResolver @Inject constructor(
         val oidcAction = oidcIntentResolver.resolve(intent)
         if (oidcAction != null) return ResolvedIntent.Oidc(oidcAction)
 
-        // External link clicked? (matrix.to, element.io, etc.)
-        val permalinkData = intent
+        val actionViewData = intent
             .takeIf { it.action == Intent.ACTION_VIEW }
             ?.dataString
+
+        // Mobile configuration link clicked? (mobile.element.io)
+        val mobileLoginData = actionViewData
+            ?.let { loginIntentResolver.parse(it) }
+        if (mobileLoginData != null) return ResolvedIntent.Login(mobileLoginData)
+
+        // External link clicked? (matrix.to, element.io, etc.)
+        val permalinkData = actionViewData
             ?.let { permalinkParser.parse(it) }
             ?.takeIf { it !is PermalinkData.FallbackLink }
         if (permalinkData != null) return ResolvedIntent.Permalink(permalinkData)

appnav/src/test/kotlin/io/element/android/appnav/intent/IntentResolverTest.kt

@@ -12,6 +12,8 @@ import android.content.Intent
 import android.net.Uri
 import androidx.core.net.toUri
 import com.google.common.truth.Truth.assertThat
+import io.element.android.features.login.api.LoginParams
+import io.element.android.features.login.test.FakeLoginIntentResolver
 import io.element.android.libraries.deeplink.DeepLinkCreator
 import io.element.android.libraries.deeplink.DeeplinkData
 import io.element.android.libraries.deeplink.DeeplinkParser
@@ -165,6 +167,7 @@ class IntentResolverTest {
             userId = UserId("@alice:matrix.org")
         )
         val sut = createIntentResolver(
+            loginIntentResolverResult = { null },
             permalinkParserResult = { permalinkData }
         )
         val intent = Intent(RuntimeEnvironment.getApplication(), Activity::class.java).apply {
@@ -182,7 +185,8 @@ class IntentResolverTest {
     @Test
     fun `test resolve external permalink, FallbackLink should be ignored`() {
         val sut = createIntentResolver(
-            permalinkParserResult = { PermalinkData.FallbackLink(Uri.parse("https://matrix.org")) }
+            permalinkParserResult = { PermalinkData.FallbackLink(Uri.parse("https://matrix.org")) },
+            loginIntentResolverResult = { null },
         )
         val intent = Intent(RuntimeEnvironment.getApplication(), Activity::class.java).apply {
             action = Intent.ACTION_VIEW
@@ -231,7 +235,8 @@ class IntentResolverTest {
     @Test
     fun `test resolve invalid`() {
         val sut = createIntentResolver(
-            permalinkParserResult = { PermalinkData.FallbackLink(Uri.parse("https://matrix.org")) }
+            permalinkParserResult = { PermalinkData.FallbackLink(Uri.parse("https://matrix.org")) },
+            loginIntentResolverResult = { null },
         )
         val intent = Intent(RuntimeEnvironment.getApplication(), Activity::class.java).apply {
             action = Intent.ACTION_VIEW
@@ -241,11 +246,29 @@ class IntentResolverTest {
         assertThat(result).isNull()
     }
 
+    @Test
+    fun `test resolve login param`() {
+        val aLoginParams = LoginParams("accountProvider", null)
+        val sut = createIntentResolver(
+            loginIntentResolverResult = { aLoginParams },
+        )
+        val intent = Intent(RuntimeEnvironment.getApplication(), Activity::class.java).apply {
+            action = Intent.ACTION_VIEW
+            data = "".toUri()
+        }
+        val result = sut.resolve(intent)
+        assertThat(result).isEqualTo(ResolvedIntent.Login(aLoginParams))
+    }
+
     private fun createIntentResolver(
-        permalinkParserResult: (String) -> PermalinkData = { lambdaError() }
+        permalinkParserResult: (String) -> PermalinkData = { lambdaError() },
+        loginIntentResolverResult: (String) -> LoginParams? = { lambdaError() },
     ): IntentResolver {
         return IntentResolver(
             deeplinkParser = DeeplinkParser(),
+            loginIntentResolver = FakeLoginIntentResolver(
+                parseResult = loginIntentResolverResult,
+            ),
             oidcIntentResolver = DefaultOidcIntentResolver(
                 oidcUrlParser = DefaultOidcUrlParser(
                     oidcRedirectUrlProvider = FakeOidcRedirectUrlProvider(),

features/login/api/src/main/kotlin/io/element/android/features/login/api/LoginEntryPoint.kt

@@ -13,13 +13,19 @@
 import io.element.android.libraries.architecture.FeatureEntryPoint
 
 interface LoginEntryPoint : FeatureEntryPoint {
+    data class Params(
+        val accountProvider: String?,
+        val loginHint: String?,
+    )
+
     interface Callback : Plugin {
         fun onReportProblem()
     }
 
     fun nodeBuilder(parentNode: Node, buildContext: BuildContext): NodeBuilder
 
     interface NodeBuilder {
+        fun params(params: Params): NodeBuilder
         fun callback(callback: Callback): NodeBuilder
         fun build(): Node
     }

features/login/api/src/main/kotlin/io/element/android/features/login/api/LoginIntentResolver.kt

@@ -0,0 +1,12 @@
+/*
+ * Copyright 2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.features.login.api
+
+interface LoginIntentResolver {
+    fun parse(uriString: String): LoginParams?
+}

features/login/api/src/main/kotlin/io/element/android/features/login/api/LoginParams.kt

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2025 New Vector Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.features.login.api
+
+import android.os.Parcelable
+import kotlinx.parcelize.Parcelize
+
+/**
+ * Parameters to start the login flow, when the application is opened
+ * from a mobile.element.io link.
+ */
+@Parcelize
+data class LoginParams(
+    val accountProvider: String,
+    val loginHint: String?
+) : Parcelable

features/login/impl/build.gradle.kts

@@ -58,6 +58,7 @@ dependencies {
     testImplementation(libs.test.robolectric)
     testImplementation(libs.test.truth)
     testImplementation(libs.test.turbine)
+    testImplementation(projects.features.login.test)
     testImplementation(projects.features.enterprise.test)
     testImplementation(projects.libraries.featureflag.test)
     testImplementation(projects.libraries.matrix.test)